GDI+ Objects: Icons

Like a bitmap, an icon is used to display graphics on window objects. While a bitmap can have any dimension the window needs, the size of an icon is limited. This is because icons assume different roles on an application.

Icons are used to represent folders in Windows Explorer and My Computer:

To create an icon, once again, you can use any application that has the capability. Normally, you can use Visual Studio .NET to create or design an icon. To do this, on the main menu of Visual Studio, you can click Project -> Add Resource… Then, in the Add Resource dialog box, you can select Icon and click New.

When you start designing an icon, you would be presented with a drawing area whose dimensions are 32 x 32 pixels. This is the size of the icon that displays as Large Icon. Here is an example from the New File dialog box Visual Studio .NET in the Templates list:

In some cases, you may allow the user to display smaller icons, which are 16x16 pixels:

To make this possible, you can associate a second icon to the 32x32 one. The application you use to design your icon should make it simple for you to add this second icon. To do this in Visual Studio, while the icon is displaying, on the main menu, you can click Image -> New Image Type... Select 16x16, 16 colors and click OK.

Whether you create only one or both versions of the icon, both are stored in a single file whose extension is .ico

1. Start a Windows Application named Resources2
2. On the main menu, click File -> New -> File...
3. In the New File dialog box, in the Templates list, click Icon File and press Enter
    
   
4. To erase the contents of the picture, on the Image Editor toolbar, click the Erase Tool and wipe the drawing area continuously until it shows only the green color
5. In the Colors Palette, click the white color
6. On the Image Editor toolbar, click the Fill Tool , and click the green area to make it white
7. On the Image Editor toolbar, click the Line button 
8. In the Colors Palette, click the blue color
9. In the empty drawing area, count 15 small boxes from the top left to the right. In the 16th box, click and drag right and down for an angle of 45˚ for 7 boxes. Release the mouse
10. Click the next small box on the right side of the top blue box then drag left and down at 45˚ for 7 boxes:
     
    
11. Using the tools of Image Editor toolbar, complete the design as follows:
     
    
12. In the Colors Palette, click the picture that has the small monitor
13. In the Image Editor toolbar, click the Fill tool and click a white area in the drawing area
     
    
14. To design the 16x16 pixel version of the icon, right-click a white area in the drawing section, position the mouse on Current Icon Image Type, and click 16x16, 16 Colors
15. Design the icon as follows:
     
    
16. To save the icon, on the Standard toolbar, click the Save All button
17. Locate the .\Resources1\bin\Debug folder of the current project and display it in the Save In combo box
18. Change the name of the file to Diamond and click Save
    

To support icons, the GDI+ library provides the Icon class. To use an icon in your application, you can first declare an Icon variable using one of the class' constructors. If the icon is stored in a file, the simplest constructor to use it has the following syntax:

Public Sub New(ByVal fileName As String)

With this constructor, the name of, or the path to, the icon file is passed as argument. After creating the icon, if you want to use only one size version, you can use one the following constructors to declare the variable:

Public Sub New(ByVal original As Icon, ByVal size As Size)
Public Sub New(ByVal original As Icon, ByVal width As Integer, ByVal height As Integer)

After initializing an Icon variable, if you want to get its dimensions, you can access its Width and its Height properties, or its Size property.

As mentioned already, there are various ways an icon can be used. For example, you can display it in a control by drawing it. To do this, you can call the Graphics.DrawIcon() method which is overloaded with two versions whose syntaxes are:

Overloads Public Sub DrawIcon(ByVal icon As Icon, _
                                                  ByVal targetRect As Rectangle)
Overloads Public Sub DrawIcon(ByVal icon As Icon, _
                                                  ByVal x As Integer, _
                                                  ByVal y As Integer)

The first version allows you to specify the location and dimensions of the icon. The second version allows you to specify only the location of the icon.

Practical Learning: Using an Icon